The explosion of growth in the portable wireless electronics industry has provided numerous challenges and opportunities for manufacturers of integrated circuits. The latest portable wireless telephony, data, and Internet access products demand greater functionality, higher performance, and lower cost in smaller and lighter formats. Additionally, wireless applications are spreading to new markets—from radar-equipped passenger vehicles to biomedical devices that, when injected or inserted, send data to a receiver outside the body. This demand has been satisfied in part by major advances in integrated circuit (IC) device technology and by the introduction of smaller packaging form factors, smaller discrete passive components, and high-density integrated circuit technologies. As more and more components are designed into an integrated circuit, the complexity of the integrated circuit is increased, thereby enabling greater functionality in the circuit. Moreover, functions that were once performed by multiple integrated circuits can often be integrated together onto the same integrated circuit, thereby reducing costs, power consumption, and size, while improving speed and interconnectivity.
Passive components such as capacitors, inductors, resistors, and other types of passive devices are increasingly incorporated into integrated circuits, thereby eliminating the need to include separate, discrete components in a circuit design that would otherwise increase circuit size, power consumption, and cost. However, the demands of smaller circuit design rules and the desire to incorporate various passive circuit components in an integrated circuit have demanded new materials, new structures and new processing techniques to be incorporated into the integrated circuit fabrication process. Integrated passive device technologies in which multiple passive devices share a substrate and packaging hold great potential for significantly reducing circuit board area and product size and weight and/or for allowing increased functionality at a given product size.
One type of passive device that is increasingly incorporated into many integrated circuit designs is a metal-insulator-metal (MIM) capacitor. A MIM capacitor typically comprises a stacked arrangement of materials that includes, in the least, top and bottom conductive electrodes incorporating a conductive material, and an intermediate insulator layer incorporating a dielectric material. MIM capacitors are often utilized, for example, in high frequency (e.g., RF) telecommunications applications such as in cell phones and other wireless devices, as well as other telecommunications products.
As the size of integrated circuits continues to shrink, conducting structures and leads fabricated within those circuits must be positioned in closer proximity to each other both horizontally and vertically. This introduces the problem of increased capacitive coupling between those structures and leads, which produces time delays and creates cross-talk between the wiring elements. RC (resistance-capacitance resonant) losses in the wiring levels of integrated circuits make significant contributions limiting the performance of the final semiconductor product. One way to reduce the capacitive coupling and RC losses is to lower the dielectric constant of the material that is used to separate the conducting leads and structures from each other. Other attempts to reduce the dielectric constant have produced methods that introduce air into the gap-filling dielectric material or totally replace the gap-filling material with air. While the use of particular materials or air voids can effectively reduce coupling and RC losses, such structures can increase fabrication complexity, and commensurately, fabrication costs of such integrated circuits.
Micro electro-mechanical systems (MEMS) components include microfabricated mechanical systems, such as switches, sensors, gyroscopes, and so forth, on a semiconductor chip. In general, MEMS technology is directed to the integration of mechanical elements, sensors, actuators, and electronics on a common substrate through the utilization of microfabrication technology. While associated electronics are fabricated using integrated circuit (IC) process sequences, the micromechanical components are fabricated using compatible micromachining processes that selectively etch away parts of a substrate, such as a silicon wafer or add new structural layers (e.g., by deposition), to form the mechanical and electromechanical devices. In this way, MEMS represents a complete system-on-a-chip, free of discrete, macro-scale, moving mechanical parts.
The development of MEMS components is growing due to their low cost, small area, and high performance. However, challenges remain in reducing the device footprint relative to the footprint achieved utilizing two-dimensional integration of integrated passive devices and MEMS components, reducing cost, and simplifying fabrication processes. Therefore, there is a tremendous need for more functional and cost-effective fabrication, packaging, and integration techniques for implementation of passive devices, reduction of capacitive coupling and RC losses between devices, and the incorporation of MEMS devices directly on or within integrated circuits.